Is it possible to get a future Amazon S3 link immediately when I start uploading the file?
Yes and no. Transloadit can perform complicated Assemblies that conditionally execute different steps. For instance, we might extract a zip, and depending on its content, do video encoding, or image resizing, or both for you. This makes it impossible to immediately predict what is going to happen, and so as it stands, we cannot immediately provide the final locations of encoded files.
If your workload is more linear and predictable, you could work around this by letting the client supply the final path where the results are saved, via Assembly Variables.
For instance, with Uppy, you could supply a form field with a UUID, and pass this into an export
Robot's path parameter, as well as save a pointer to your database. This way, you can
immediately know the final location of your uploaded file.